Cold Storage Control Measure for TRUs

This page last reviewed January 13, 2016

cold-storage-tru Background:

California has recently set new targets for reducing pollution, including decreasing greenhouse gas (GHG) emissions 40 percent below 1990 levels by 2030, 80 percent by 2050, and cutting petroleum use by cars and trucks by up to half from current 2015 levels by 2030.  Improving freight efficiency and transitioning to zero or near-zero emission technologies will help achieve these goals by reducing GHG emissions as well as criteria pollutant emissions (e.g. nitrogen oxides, non-methane hydrocarbons, and particulate matter).

TRUs are defined as refrigeration systems that are powered by internal combustion engines. They control the environment of temperature-sensitive products in refrigerated trucks, trailers, railcars and shipping containers.  They may be capable of cooling or heating.  TRUs are used to transport and store many products, including, but not limited to food, pharmaceuticals, plants, medicines, blood, chemicals, photographic film, art work, and explosives.  Transport refrigerators (TR) are similar in most regards to TRUs; but they do not have an internal combustion engine inside the unit housing.

Some companies use TRUs for extended cold storage during the four- to six-week period before major holidays and events.  Distribution centers and grocery stores are known to run out of cold storage space in their buildings, so they store overflow goods in TRU-equipped trucks and trailers outside the grocery stores and distribution centers. Some distribution centers also operate in a way that causes TRU-equipped trucks and trailers to be parked or queued for extended times, waiting for an open loading dock space or manpower to unload goods, or waiting for dispatch or driver pick-up.  These operations sometimes continue for several days.  A few DCs are using refrigerated trailers equipped with all-electric stationary TRs ( e.g. Carrier Transicold's Vector 8100) that are plugged into the grid while in use.

Near-Term Regulatory Concepts:

In April 2015, ARB staff released a Sustainable Freight Discussion Document which discussed a potential regulation to limit stationary operation of internal combustion-driven TRUs for cold storage and incentives to install infrastructure at affected locations.  Stationary operating limits would be phased in over time at grocery stores and distribution centers.  Later phases may further limit the stationary operating time and affect more types of facilities or locations.  The regulation would encourage more energy-efficient operations that reduce emissions of GHGs and criteria pollutants from internal combustion engine-driven refrigeration systems.  Compliance could be achieved several ways:

  1. Use electrically-driven TRs or TRUs that plug into grid power while stationary (e.g. all-electric TRs, hybrid-electric TRUs, or TRUs equipped with electric standby; 
  2. Use cryogenic TRs (e.g. using liquid nitrogen, liquid carbon dioxide, or liquid air to cool the cargo space), 
  3. Use adequately sized cold storage facilities,
  4. Use effective load scheduling and dispatch systems and procedures.

This near-term GHG control measure is only in the preliminary concepts phase, and workshops to discuss the concepts with stakeholders will begin early 2016.  In addition to producing near-term GHG and criteria pollutant emission reductions, the proposed regulatory measure could help to advance zero and near-zero emission transport refrigeration system commercialization by increasing the earlier penetration of infrastructure that will be needed for those technologies.  The same infrastructure that is used to comply with the near-term GHG control measure could be used as zero and near-zero emission technologies become commercially ready.  

What's New

Posted October 12, 2015

Proposition 1B funds are currently available for the replacement of existing diesel TRUs with zero-emission TRs, as well as the purchase and installation of electric and/or cryogenic infrastructure.  Such infrastructure could be used for zero-emission units, or hybrid electric TRUs and TRU equipped with electric standby. Solicitations are open at certain California air districts, which are listed at ARB's Goods Movement Website.

Posted August 27, 2015

Zero Emission Transport Refrigerator Technologies List.  
This list includes a brief technology description, manufacturer's company name, brand or model, website address, and contact information.  A zero emission transport refrigerator must not be powered by an internal combustion engine in any way.  Electric power for refrigeration system compressor, fans, and controls may come from on-board batteries, provided they are not re-charged by an alternator or generator that is driven by the vehicle engine or powertrain, trailer wheels, trailer axle/differential, or any other contrivance that adds to the vehicle drag and/or engine load.  Examples of zero emission TRs include, but are not limited to, TRs with refrigeration system and/or fans that are powered by batteries when on-road, and use battery chargers that are plugged into the electric power grid while stationary or connected to on-board solar panels.

Posted July 31, 2015

The California Air Resources Board (ARB/Board) announces the release of the draft document “Technology Assessment: Transport Refrigerators." The draft technology assessment can be viewed and downloaded from the ARB’s technology and fuels assessment webpage at:

Interested parties are encouraged to submit comments on the draft technology assessment through the technology and fuels assessment web page for public comments at:  We request to receive comments within 30 days of the posting of this draft assessment, if possible.

If you have questions regarding the draft technology assessment, please contact Mr. Rodney Hill, Staff Air Pollution Specialist, at 916-327-5636, or email to 

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